Telephone-exchange system.



L. H. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION man SEPT. I. 1915.

1,227,153. Patenfed M3y22,1917.

W/In e65 es: //1 venl'or: g Lew/J /7. Johnson.

Is FETERS co. PNOTO-LITNO" wAsumamu, n c.

LEWIS HOWES JOHNSON, OF BLOOMFIELD, NEW' JERSEY, ASSIGNOIR, BY MESNE ASSIGNMENTS, TO W ESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORA- TION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

, Specification of Letters Patent. I Pa tentedlw ay 2 2, 191?,

I Application filed September 7,1515. Serial No. 49,231. 1

To all whom it may concern:

Be it known that I, LEWIS Howns J 01in SON, a citizen of the United States, residing at Bloomfield, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephoneeither of the connected subscribers signal the operator by flashing the respective supervisory signal device, it is impossible for the operator to telephonically connect the central oflice telephone set to the line with-' out first withdrawing one or theother of the plugs from the jack. This results in consid- I erable confusion and is objectionable, due to the fact that the connection between the two subscribers is interrupted.

It is an object of this invention to provide a telephone exchange system in which the above mentioned disadvantage is overcome, and in which, while the operators telephone set is normally disconnected from an established connection, still either party to an established connection may permit the operator to listen-in.

In accordance with a feature of this invention, there is provided the usual link cir cuit for interconnecting the subscribers and an operators telephone set which is nor mally disconnected from the link circuit forming a portion of an established connection. A relay which'is associatedwith. the link circuit is controlled from either of the connected substations and cooperates with operators control switohing means to connect the operators telephone set to the link circuit. i

For a more complete understanding of this invention reference isi'macle tothe 'accompanying 'drawing showing one embodiment thereof, and wherein all apparatus is shown in its normal and unactuated condition.

In the drawing there is shown the usual subscribers stations A and B, terminating ing of relay 26.

central oflice at which is located a cord circuit C for interconnecting the stations.

Subscriber A, wishing to converse with sub- 7 scriber B, signals the operator in the usual a manner. The operator answering, inserts the answering plug into the jack of the c'alling line, causing the operation of supervisory relay 5 included in bridge of the talking strand of the cord circuit; also operates cutoff relay 6; Relay 5, in operating, causes the operation of listening relay 7 ,which connects the operators telephone set across the talk ing strands of the cord circuit. The opera tor, finding that subscriber A desires to be connected with subscriber B, inserts the call ing plug of the-cord circuit into-the jack of Bs line, thereupon operating relay Sand cutofi'relay 9. The operation of relay Sreleases listening'relay 7, thereby disconnecting the operators telephone set from the talking I A strands of the/cord circuit, and lights calling supervisory lamp 10.- The operator byv actuating ringing key 16 causes the opera tion of the signal receiving device ,15' at sta tion B. Inresponse to the slgnal, subscriber B removes the receiver from the switchhook,

thereby operating supervisory relay 17 which eifaces the calling supervisory signal 10 and completes the circuit for relay 18.

Relay'lS thereupon operates and completes a locking circuit for itself from battery,

through contact 22 of key 23, and. contact 24 and winding of relay 18 to ground. The operation of relay 18 alsoopens at contact 25 the short-circuit about the left-hand windcorresponding supervisory lamp to flash.

When the line circuit of either A or B is opened by the first downward movement of the .switchhook, the respective supervisory relay is denergized, whereupon a circuit is completed for relay 26 from battery, through one or the other of the supervisory lamps, the back contact of one or theother of the supervisory relays, the left-hand winding of relay26, thecontact 80 of key 23, and the upper contact of relay 8 to ground. Relay 26 operates, completing a locking circuit for itself, which is under the joint control of key 23 and relay 7. The operator havingobwinding of relay 7 to ground.

served the flashing of thesupervisory lamp, actua'tes key23, thereby causing theoperation ofthe listening-relay-7 which connects the operators. telephoneset to the talking strands of the cord circuit. This energizing circuit of relay 7 may betraced from battery,

through contact 31 of relay 26-, both windings thereof, contact 32 of key 28, and the When key 23'is actuated, the locking circuit ofrelay 18 is opened, whereupon it releases. Upon the operation of listening relay 7 inrseries with relay 26, a locking circuitis completed for the formerwhich may be traced from the battery through contact 35 of key 23;,and

contact 36 and winding of relay 7 to ground. This short circuits and releases relay 26. The operator, after conversing with the connected subscriber who has signaled the central oli'ice, releases key 23, whereupon listening relay 7 is deenergized. VVhenthe conversation between the subscribers is com- .pleted, the restoration of the rec'eiversto the s'witchhooks causes 1both supervisory lamps to be lighted to furnish a disconnect signal to the operator. Both .plugs are removed from the jacks, whereupon all apparatus returns to normal position.

It will benoted from. the above descrip I tion that by utilizing the present invention a telephone exchange system is provided with secret service, that is, an operator cannot listen to the conversation of both parties to an established connection. However,

the operator may connect her telephone set tow the talking strands of the cord circuit whenei er either of the connected subscribers desires to communicate with the operator.

l/Vhat is claimed is; l. A telephone exchange system comprising two telephone lines terminating at a central oflice, a link circuit connecting the lines together, an operators telephone set normally disconnected from the link circuit, a

listening relay for connecting the operators telephone set with the link circuit, a relay in the link circuit controlled over one of the connected lines, and an operator-controlled switch when actuated cooperating with the second mentioned relay when energized to cause the operation of the listening relay. 7

.2. A telephone exchange system comprising two telephone lines terminating at a central office, a'link circuit connecting the' lines together, an operators telephone set normally disconnected from the link circuit,

a relay'in the'link circuit controlled over; a

connected-telephone line and energized upon 7 the opening of the line, a locking circuit for the relay established upon the energization thereof, andan operator-controlled switch when actuated cooperating with the energized relay to cause the connection of the. operators telephone set with the link circuit.

In a telephone"exchange system, in

combination subscribers llines terminating at a central oiiice, a link circuit thereat in} terconnecting said'lines, an operators 'telephone set normally.disconnected from said link circuit forming a portion of an established connection,a listening relay controlling the connection of said set to said link circuit, a supervisory relay associated with sa1d link circuit controlled from'the' connected substation, a relay associated with said link circuit energizedupon the deenergization of said supervisory relay, the energization of said relay cond tioning said hetening relay forv operation, and operator controlled switchingmeans actuated to cause i 1 the operation ofsaid conditioned listening relay.

tral othce,a link circuit connecting the lines together, an operators telephone set nor- 4. A telephone exchange system comp-ris mg two telephone lines terminating at a cenmally disconnected from the link circuit, a.

supervisory relay inthe link circuit, a second relay therefor energizedupon the jdeenergi zation of the supervisory relay, an 'operator 7 controlled switch, and alistening relay enmally disconnected from the link circuit, a supervisory relay in the link circuit, a sec ond relay therefor energized upon the deenergization of the supervisory relay, an operator-controlled switch, a listening relay for connecting the operators telephone set with the linkcircuit, and an operating circuit for the listening relay completed upon the energization of the second relay and the 1 7 actuation of the switch.

6. In a telephone exchange system, in

combination subscribers lines terminating at a central office, a link circuit thereat interconnecting said lines, an operators telephone, set normally disconnected from said link circuit forming a portion of an established connection,a listening relay controlling the connection of said set to said link circuit, a supervisory relay associated with 7 each end of said link circuit and controlled. from the respective connected substat1ons,a third relay associated with said link circuit of said supervisory relays, acircuitfor' said listening relay open at two points, one ofv which is closedby the energization of said third relay, and operator controlled switching means, the actuation of which completes the circuit of said listening relay.

7. In a telephone exchange system, in

energized upon the deenergization of either V ofiice normally excluding the operators telephone set from the link circuit While the connected line circuits are closed at the subscribers substations, and means controlled from the subscribers station of either connected line circuit for rendering the excluding means inefi'ective to permit the connection of the operators telephone set to the link circuit While the connected line circuits are closed at the subscribers stations.

In Witness whereof, I hereunto subscribe my name this 3rd day of September A. D.,

LEWIS HOWES JOHNSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 0. 

